1. Field of Invention
The present invention relates to a one-way wrench and, more particularly, to a multi-mode one-way wrench.
2. Related Prior Art
A one-way wrench (or “ratchet wrench”) includes a head, a toothed wheel placed in the head, and a pawl placed in the head. The head can be rotated in an active direction to bring the pawl into engagement with the toothed wheel so that the head rotates the toothed wheel via the pawl. The head can be rotated in an idle direction to allow the pawl to rattle on the toothed wheel so that the head does not rotate the toothed wheel in the idle direction.
In operation, the toothed wheel is engaged with a nut for example. The head is rotated in the active direction to rotate the toothed wheel for an angle, and the head is rotated in the idle direction for an adequate angle before the head is rotated in the active direction again to rotate the wheel. This process is repeated so that the nut is engaged with a screw or removed from a screw. Such a one-way wrench is particularly useful in a limited space.
The head must be rotated in the idle direction for at least a minimum angle before the head can rotate the toothed wheel in the active direction again. The more the teeth of the toothed wheel are, the smaller the minimum angle is, i.e., the more convenient the operation of the one-way wrench is. For example, the minimum angle is 10° where the toothed wheel includes 36 teeth but only 5° where the toothed wheel includes 72 teeth. However, the more the teeth are, the smaller and hence weaker they are. It is difficult to increase the convenience without jeopardizing the strength in a conventional one-way wrench.
To reach a good balance between the convenience and strength, the applicant has invented a one-way wrench and filed applications such as European Patent Application No. 12195169.3, U.S. patent application Ser. No. 13/691,477, Japanese Patent Application No. 2013-170474, Chinese Patent Application No. 201210507001.6 and Taiwanese Patent Application No. 101139643.
Therefore, the present invention is intended to obviate or at least alleviate the problems encountered in prior art.